Gallium nitride (GaN)-based devices such as light-emitting diodes (LEDs) and High Electron Mobility Transistor (HEMT) devices may be grown on a variety of substrates such as bulk GaN, sapphire, patterned sapphire (PSS), silicon carbide, silicon, etc. However, GaN-based devices grown on bulk GaN substrates significantly out-perform similar devices grown on other types of substrates. Specifically, GaN-based devices grown on bulk GaN substrates exhibit superior crystal quality and low GaN defect density as compared to similar devices grown on other substrates. This superior crystal quality allows GaN-based devices formed on bulk GaN substrates to operate at substantially higher current densities resulting in two to four times the light output (lumens) per unit area of similar GaN-based devices formed on traditional substrates.
Due to cost constraints, bulk GaN substrates are not economically viable for a majority of GaN-based device applications. A variety of challenges must be addressed to engineer high-performance, economically viable substrates.